Question

Which one of the following ores is best concentrated by froth flotation method?
(a) Siderite
(b) Galena
(c) Malachite
(d) Magnetite

Answer 1

Hint: Froth flotation is the method used for the concentration of ores i.e. to remove the impurities from ore and obtain pure ore free from impurities and this method is mainly used for the concentration of impurities from sulphide ore.

Complete answer:
Froth flotation is a technique which is commonly used in the mining industry and in this method, materials are separated on the basis of their hydrophobic (means they are water repelling) and hydrophilic (water loving) nature and is most commonly used method for the separation of sulphide ores. In this, the impurities are removed from the mineral ore and the pure minerals are extracted from it.
It is based on the principle of the difference in the wetting properties(the ability of the solute particles to get dissolve in the water ) of the ore and gangue particles and in this, ore is wetted by oil( pine oil)(hydrophobic in nature) and gangue particles(i.e. the impurities present in the ore) are wetted by water( hydrophilic in nature).
In this method, first of all the ore is crushed into small pieces and after that it is mixed with the collector i.e. pine oil( the collectors enhances the non-wettability of ores i.e. it prevents the ore to not to dissolve in the solvent, the water )and a slurry is formed which is then it is put into the water containing container and a mixture is formed of ore, oil and water. And the impurities present in the and a vacuum is created inside the water container resulting in the formation of froth on the surface of the water.
The ore particles coated with the pine oil being lighter in nature floats on the surface of the froth and the gangue particles being heavier in nature settles down in the water. Some stabilizers like aniline, cresols etc. are added to the froth to maintain the froth for some time over the water surface and after that, the ore along with the froth is taken out of the container and the gangue particles settled down in water are left behind. After that, the froth is dried and the ore is collected from it and is now free of impurities.
 So, from the given options Galena is the ore of sulphide and is, therefore, separated by this froth flotation method.

Hence, option(b) is correct.

Note: Collectors i.e. the pine oil is always added to the ore to enhance its wettability otherwise, in its absence, the ore will also get dissolved in the solvent water and it will then become difficult to separate impurities from it.